Muscle Strength Loss in the Lower Limb After Total Knee Arthroplasty

Abstract

This study aimed to examine functional mobility and strength loss in the ankle plantarflexors and dorsiflexors and knee extensors and flexors after total knee arthroplasty. This was a prospective, longitudinal cohort study. Maximal voluntary isometric contractions and gait speed assessments were performed before and after total knee arthroplasty. Twenty patients undergoing primary total knee arthroplasty were followed. Repeated-measures analysis of variance results indicated an effect of time on muscle strength, with all muscle groups being significantly weaker (knee extensors, P < 0.001; knee flexors, P < 0.001, ankle plantarflexors, P = 0.004; ankle dorsiflexors, P < 0.001) 1 mo postoperatively. Knee extensors were 42% weaker than preoperative levels, and knee flexors were 34% weaker, whereas the ankle plantarflexors were 17% weaker, and the dorsiflexors were 18% weaker. Three and 6 mos after surgery, strength in all muscle groups was similar to preoperative levels (P > 0.05 for all muscle groups). Patient function followed a similar trend, with patients walking slower 1 mo postoperatively (P < 0.001) and recovering to preoperative levels by 3 and 6 mos after surgery (P > 0.05). Patients may benefit from early postoperative rehabilitation, including strengthening of the plantarflexors and dorsiflexors, although strengthening of the quadriceps and hamstrings muscles should continue to be a priority.